Method IV 



35 



per cent., 70 per cent., 95 per cent.), 3 or 4 minutes in each, up 

 to absolute alcohol, where they should remain for 10 minutes; 



They are then cleared in chloroform for 10-15 minutes and 

 mounted in balsam as in I, 16, p. 19. 



After reduction and washing, the sections will permit of 

 counterstaining, if desired. An immersion of 10-20 minutes in 

 a I per cent, aqueous solution of safranin is recommended for 

 this purpose. Often it is best not to counterstain. Neurofibrillae 

 are more distinct without it. 



If successful, the nerve-fibrils of the cell or terminal branches 

 of the axone appear dark violet to black ; other structures, pink 

 to purple. 



Amongvertebrates, the cells of the spinal cord of the calf and 

 the large cells in the spinal cord of the goose fish [Lophius) are 

 especiaUy recommended. 



For invertebrates, Apathy recommends fixing the fresh tissue 

 for 6-12 hours in the simple saturated aqueous solution of cor- 

 rosive sublimate. 



Corrosive sublimate (Hg CI 2), 6 g. 

 Distilled water, 100 cc. 



Heat till dissolved and let cool before using. Then the tissue 

 is washed out with the iodine solution (B). This and the suc- 

 ceeding treatment are the same as for vertebrates. 



Apathy obtained some of his best results on the medicinal 

 leech {Hirudo medicinalis) . 



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